Touch sensors, for example capacitive touch sensors, used in touch sensitive display systems are subject to noise from nearby display scanning circuitry. Noise makes touch detection less reliable. In some touchscreen designs, stack materials between the touch electrodes and the display driver circuitry offer a degree of noise screening. However, enhancing this by providing additional screening layers can be costly and it tends to contribute at least some additional thickness to the panel. Moreover, certain types of displays use driver circuitry that utilizes relatively high switching voltages. For example, electrophoretic panel screens tend to use high switching voltages (for example in the range of 50-100 volts) and these generate significant amounts of noise at the output of nearby touch electrodes. Known shielding approaches may not provide sufficient shielding capability with respect to noise caused by such high switching voltages.
In other types of touchscreens, for example designs using LCD displays in combination with a stack of touchscreen layers, high sheet resistance of stack materials like indium tin oxide results in noise coupling through to the receive electrode layer (so-called “punch through” effect). Techniques based on filtering can reduce noise but tend to slow down response times and lead to increased power consumption.